Atmos. Chem. Phys. Discuss., 7, 12381-12415, 2007
www.atmos-chem-phys-discuss.net/7/12381/2007/
doi:10.5194/acpd-7-12381-2007
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Optical particle counter measurement of marine aerosol hygroscopic growth
J. R. Snider1 and M. D. Petters2
1University of Wyoming, Department of Atmospheric Science, Dept. 3038, 1000 East University Avenue, Laramie, WY 82071, USA
2Colorado State University, Department of Atmospheric Science, 1371 Campus Delivery, Fort Collins, CO 80523-1371, USA

Abstract. A technique is developed for the determination of the hygroscopic growth factor of dry particles with diameter between 0.3 and 0.6 µm and is applied to measurements made during the second Dynamics and Chemistry of Marine Stratocumulus experiment. Two optical particle counters are utilized, one measures the aerosol size spectrum at ambient relative humidity and the other simultaneously dries the aerosol prior to light scattering detection. Growth factors are based on measurements made in the region of the Mie scattering curve where scattered light intensity increases monotonically with dry and wet particle diameter, i.e. D<0.9 µm. Factors influencing the accuracy of the measurement are evaluated, including particle drying, refractive index and shape. Growth factors at 90±3% ambient relative humidity in marine airmasses 400 km west of San Diego, California range between 1.5 and 1.8. This suggests that a significant fraction of the particle mass, between 40 and 70%, is either non-hygroscopic or weakly hygroscopic.

Citation: Snider, J. R. and Petters, M. D.: Optical particle counter measurement of marine aerosol hygroscopic growth, Atmos. Chem. Phys. Discuss., 7, 12381-12415, doi:10.5194/acpd-7-12381-2007, 2007.
 
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